Daemons

Systemd

systemd is the default init framework, replacing initscripts. The services which are started by systemd can be found in the subfolders of /etc/systemd/system/. Services can be enabled using the systemctl command. For more information about systemd and how to write autostart scripts for it, see at systemd. To autostart scripts for specific users, see systemd/User.

/etc/profile

Upon login, all Bourne-compatible shells source /etc/profile, which in turn sources any readable *.sh files in /etc/profile.d/: these scripts do not require an interpreter directive, nor do they need to be executable. They are used to set up an environment and define application-specific settings.